Employee Benefit Plans, Pre-Tax Amounts in Accumulated Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Pension Plans [Member]
Pension and Other Postretirement Benefit Plans Accumulated Other Comprehensive Income (Loss), before Tax
Prior service cost (credit)	$ 21	$ 16
Net actuarial loss	882	681
Accumulated other comprehensive (income) loss	903	697
Other Postretirement Benefit Plans [Member]
Pension and Other Postretirement Benefit Plans Accumulated Other Comprehensive Income (Loss), before Tax
Prior service cost (credit)	(81)	(103)
Net actuarial loss	34	50
Accumulated other comprehensive (income) loss	$ (47)	$ (53)